The return of over 5,000 kokanee salmon to Kluane National Park in southwest Yukon in 2015 was cause for excitement after the population was nearly declared extinct in 2009.

“Historically about 3,000 kokanee return to the spawning beds, but in the early 2000’s the population plummeted to several hundred, and in 2009 we only counted 20 fish,” says Carmen Wong, ecological team leader with Parks Canada. “So the return of this many fish is truly astounding.”

The reason for the salmon’s return is unclear, but the leading hypothesis is that it’s climate driven. Sockeye salmon—which have the same genetic make up as kokanee salmon—also experience crashes and booms in their population which have been attributed to changes in water temperatures. Wong says this has led researchers to believe the same thing is happening with the kokanee.

“What’s really interesting about this population is it went to near extinction yet came back with basically no management, so we’re really going to put a lot of effort into figuring out if the role of climate can explain this” she says.

The fish will be counted again in August, and although the 2015 surge in numbers is promising, Wong says it’s too early to consider the population stable.

“It was only six years ago that we counted only 20 fish, so we’re nowhere near in the clear yet for declaring the recovery of this population,” she says. “But we do have reports that fishermen are catching and returning them to the water, so that’s a good indication that there are still lots of them around.”

While kokanee can be found across British Columbia and the western United States, this population is unique because it’s one of two wild populations in the Yukon, and is the only wild population found in a national park.